The disclosure of Japanese Patent Application No. 2000-312386 filed on Oct. 12, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a sensor outputting a trigger for operating a start preparation apparatus before a main body of an internal combustion engine is started, and preferably to a control device of an internal combustion engine provided with a seating switch, a door opening and closing switch and the like, and a method of judging a failure of a sensor.
2. Description of Related Art
In an internal combustion engine for a vehicle which has been conventionally known, an oxygen sensor provided in the internal combustion engine detects an oxygen concentration contained in an exhaust gas. The detected oxygen concentration is used for air-fuel ratio feedback control. The oxygen sensor is heated by energizing an electric current to a heater provided with the oxygen sensor, and is activated by this heating. In order to execute the air-fuel ratio feedback control from the first time of the start of the internal combustion engine, it is necessary to heat the oxygen sensor before starting the internal combustion engine.
A technique for heating before the starting is disclosed in Japanese Patent Application Laid-open Publication No. 5-202785. In the publication, it is disclosed that the heating is started on the basis of opening and closing of a door, an act of sitting in a seat or the like applied as the triggers.
However, in the case of failure of the sensor outputting the triggers, the heating or the like before starting is not executed, so that the control of the internal combustion engine is not optimized. Accordingly, if a sensor of this type fails, it is desirable to detect the failure.
An object of the invention is to provide a control device of an internal combustion engine which can detect whether or not a specific sensor giving a trigger to a start preparation apparatus before starting a main body of the internal combustion engine has failed, and a method of judging a failure of the sensor.
In accordance with a first aspect of the invention, a control device of an internal combustion engine is provided with an internal combustion engine main body mounted to a vehicle, a start preparation apparatus operating on the basis of an output from a specific sensor given as a trigger at least before the internal combustion engine main body starts, and a failure judging device for judging that the sensor has failed in the case that an output of the sensor at a time when the vehicle is running is different from a defined value.
In the case that the output of the sensor at a time when the vehicle is running is different from the defined value, it is possible to judge that the sensor has failed. It is preferable that the defined value coincides with an output of the sensor at a time when the vehicle is running when the sensor is normal.
In accordance with a second aspect of the invention, a control device of an internal combustion engine is provided with an internal combustion engine main body mounted to a vehicle, a start preparation apparatus operating on the basis of an output from a specific sensor given as a trigger at least before the internal combustion engine main body starts, and a failure judging device storing whether or not the start preparation apparatus is operated before the start and judging that the sensor has failed in the case that the operation of the start preparation apparatus is not stored.
That is, in the case that the operation is not stored, that is, in the case that no history is stored, it is possible to presume that the trigger is not generated due to failure of the sensor, so that in this case, it is also judged that the sensor has failed.
Further, it is preferable that failure of the sensor is determined when a number of times that the failure is judged reaches a plurality of predetermined number of times.
In particular, if the failure of the sensor is determined in the case that the number of times that the failure is judged continuously reaches a plurality of predetermined number of times, it is possible to more reliably determine the failure.
It is preferable that the start preparation apparatus is a heater provided with the internal combustion engine.
It is preferable that the heater is structured such as to heat an oxygen sensor detecting an oxygen concentration in an exhaust gas of the internal combustion engine according to the operation of the heater.
It is preferable that the sensor is an opening and closing switch detecting opening and closing of a door of a vehicle. That is, since the door is closed at a time when the vehicle is running, a failure diagnosis can be executed so that in the case that the output of the opening and closing switch indicates xe2x80x9cclosedxe2x80x9d, the sensor is normal, and in the case that the output of the opening and closing switch indicates xe2x80x9copenxe2x80x9d, the sensor is abnormal.
It is preferable that the sensor is a seating switch detecting whether or not a driver sits in a seat of the vehicle. That is, since the driver is seated therein when the vehicle is running, a failure diagnosis can be executed so that in the case that the output of the seating switch indicates xe2x80x9cseatedxe2x80x9d, the sensor is normal, and in the case that the output of the seating switch indicates xe2x80x9cnot seatedxe2x80x9d, the sensor is abnormal.